Purification Methods
The lower boiling fraction from the preceding spinning band column fractionation of the commercial cis-trans-mixture (~ 20:60; see the cis-isomer above) solidifies readily (m 48o), and the receiver has to be kept hot with warm water. It is further purified by conversion to the hydrochloride m 285-286o after recrystallisation from EtOH/AcOEt. This has IR (KBr) 2920, 2760, 2578, 2520, 1580, 1455, 1070, 1050, 975, 950, 833 cm-1 .max The free base is prepared as for the cis-isomer above and distilled; and has IR (film, at ca 50o) 2905, 2840, max 2780, 1447, 1335, 1305, 1240, 1177, 1125, 987, 900, 835 cm-1 . The 1HNMR in CDCl3 is characteristically different from that of the cis-isomer. [Armarego J Chem Soc (C) 377 1967, Hückel & Stepf Justus Liebigs Ann Chem 453 163 1927, Bailey & McElvain J Am Chem Soc 52 4013 1930, Prelog & Szpilfogel Helv Chim Acta 28 1684 1945, Beilstein 20 H 157, 20 I 35, 20 II 72-73, 20 III/IV 2017.]
